The present invention refers to the deposition of thin film coatings produced by the plasma-activated chemical vapor deposition of volatile fluorinated cyclic siloxanes having the structure [RR'SiO].sub.x, where R is an alkyl group with 1-6 carbon atoms, R' is a fluorinated alkyl group with 3-10 carbon atoms, the carbon in the alpha and beta positions with respect to the silicon atom is hydrogenated and x is 3 or 4. The process consists of introducing vaporized siloxane into a deposition chamber containing the substrate to be coated. The reaction of the vapor is then induced by means of a plasma that has been excited by radio-frequency (RF) electric field. The particular coatings thus produced have useful physical properties.
Plasma-activated chemical vapor deposition of thin films using gases or chemical vapors is a well-known technique in the field of film formation for coating various substrates. Numerous chemical vapors useful in this technique which allow the formation of various films are known. For example, thin films containing silicon and carbon can be obtained by means of plasma-activated chemical vapor deposition from mixtures of silane (SiH.sub.4)-methane or silane-ethylene, as well as from mixtures of tetramethylsilane-argon. Similarly, the production of silicon oxide-type films from silanes (for example, SiH.sub.4, H.sub.2 SiCl.sub.2, etc. ) mixed with an oxidizing gas (for example, air, oxygen, ozone, NO.sub.2, etc. ) is known.
What was not yet known, however, is that volatile fluorinated cyclic siloxanes could be used as gaseous sources for plasma-activated chemical vapor deposition to obtain fluoropolymer films containing silicon.